1. Field of the Invention
The present invention relates to a mobile node, a mobile communication system, and a communication control program.
2. Related Background Art
FIG. 19 is a block diagram showing an example of a first mobile communication system in which a mobile node is a mobile host. In FIG. 19, MH indicates a mobile host, HA indicates a home agent, AR indicates an access router, and CH indicates a correspondent host. As shown in FIG. 19, a mobile communication system 101 comprises a mobile host 103, a home agent 105, a plurality of access routers 107, 109, a correspondent host 111, and an IP network 113.
The home agent 105 provides the mobile host 103 with a home link. The access routers 107, 109 provide the mobile host 103 with wireless links (to be referred to as “external links” hereinafter) other than the home link. The correspondent host 111 performs communication with the mobile host 103.
The mobile host 103 uses a home address on a home link, and on an external link uses the home address and a care-of address having a link prefix for each external link. The mobile host 103 notifies the home agent 105 of binding which states “home address of this node” and “care-of address obtained by connection link”, and the home agent 105 stores this binding. When the home agent 105 receives a packet addressed to the home address of the mobile host 103, the home agent 105 creates an IP packet addressed to the bound care-of address, stores this packet in a payload portion, and forwards the packet to the mobile host 103. Having received the forwarded packet, the mobile host 103 extracts the original packet from the payload portion. The internal packet is addressed to the mobile host 103 and can therefore be received thereby.
Next, state transitions of a conventional mobile host during a hand-off in the mobile communication system 101 of the aforementioned constitution will be described on the basis of FIG. 20. It is assumed here that the mobile host 103 communicates with the correspondent host 111 in a stationary network.
As shown in FIG. 20, the state transitions of the mobile host 103 during a hand-off are divided into four.
State I: the link layer of the mobile host 103 is connected to the access router 107. The care-of address of the mobile host 103 is set at CoA1, and a default router is set to the access router 107.
State II: the link layer of the mobile host 103 switches connection point from the access router 107 to the access router 109. The period during this connection point switching is known as a link layer disconnection period. At this time, the care-of address of the mobile host 103 is CoA1, and the default router is the access router 107.
State III: the link layer of the mobile host 103 is connected to the access router 109. At this time, the care-of address of the mobile host 103 is still CoA1, and the default router is still the access router 107. This state continues until the mobile host 103 receives a router advertisement from the access router 109 and switches the default router from the access router 107 to the access router 109.
State IV: this is the state which follows reception of the router advertisement from the access router 109, alteration of the care-of address of the mobile host 103 to CoA2, and switching of the default router from the access router 107 to the access router 109. At this time, the link layer connection point and the default router are both the access router 109. The mobile host 103 notifies the home agent 105 of binding for the home address and new care-of address CoA2 by means of a binding update packet.
The link layer connection points, default routers, and care-of addresses in these states I to IV are summarized in Table 1.
TABLE 1LINKLAYER CONNECTIONDEFAULTSTATEPOINTROUTERCARE-OF ADDRESSIAR107AR107CoA1IINONE(BREAK)AR107CoA1IIIAR109AR107CoA1IVAR109AR109CoA2
As shown in FIG. 20, the state transitions of the home agent 105 during a hand-off are divided into two.
State A: binding for the home address and care-of address CoA1 of the mobile host 103 is recorded in the home agent 105. The home agent 105 transfers packets addressed to the mobile host 103 transmitted from the correspondent host 111 to the care-of address CoA1. This state continues until a binding update packet notifying the home address and new care-of address CoA2 is received from the mobile host 103.
State B: binding for the home address and new care-of address CoA2 of the mobile host 103 is recorded in the home agent 105. The home agent 105 transfers packets addressed to the mobile host 103 transmitted from the correspondent host 111 to the new care-of address CoA2.
The bound care-of addresses in these states A and B are summarized in Table 2.
TABLE 2BOUNDCARE-OFSTATEADDRESSACoA1BCoA2
FIG. 21 is a block diagram showing an example of a second mobile communication system in which a mobile node is a mobile router. In FIG. 21, SH is a stationary host, MR is a mobile router, HA is a home agent, AR is an access router, and CH is a correspondent host. As shown in FIG. 21, a mobile communication system 201 comprises a mobile router 203, a stationary host 205, the home agent 105, the plurality of access routers 107, 109, the correspondent host 111, the IP network 113, and a mobile network 207.
The home agent 105 provides the mobile router 203 with a home link. The access routers 107, 109 provide the mobile router 203 with external links other than the home link. The mobile network 207 moves while maintaining the connection relationship between its internal nodes (the mobile router 203 and the stationary host 205). The correspondent host 111 performs communication with the nodes on the mobile network 207.
The mobile router 203, which is a gateway router for the mobile network 207, uses a home address on a home link, and on an external link uses the home address and a care-of address having a link prefix for each link. The mobile router 203 notifies the home agent 105 of binding which states “home address of this node and network prefixes within mobile network 207” and “care-of address obtained by connection link”. The home agent 105 stores the binding received from the mobile router 203. When the home agent 105 receives a packet addressed to the home address of the mobile router 203 or a packet addressed to an address belonging to a network prefix in the mobile network 207, the home agent 105 creates an IP packet addressed to the bound care-of address, stores this packet in a payload portion, and forwards the packet to the mobile router 203. Having received this forwarded packet, the mobile router 203 extracts the original packet from the payload portion, and if addressed to another host within the mobile network 207 (the stationary host 205), the mobile router 203 routes the packet within the mobile network 207.
Next, state transitions of a conventional mobile router during a hand-off in the mobile communication system 201 of the aforementioned constitution will be described on the basis of FIG. 22. It is assumed here that the stationary host 205 within the mobile network 207 communicates with the correspondent host 111.
As shown in FIG. 22, the state transitions of the mobile router 203 during a hand-off are divided into four.
State I: the link layer of the mobile router 203 is connected to the access router 107. The care-of address of the mobile router 203 is set at CoA1, and a default router is set as the access router 107.
State II: the link layer of the mobile router 203 switches connection point from the access router 107 to the access router 109. The period during this connection point switching is known as a link layer disconnection period. At this time, the care-of address of the mobile router 203 is CoA1 and the default router is the access router 107.
State III: the link layer of the mobile router 203 is connected to the access router 109. At this time, the care-of address of the mobile router 203 is still CoA1, and the default router is still the access router 107. This state continues until the mobile router 203 receives a router advertisement from the access router 109 and switches the default router from the access router 107 to the access router 109.
State IV: this is the state which follows reception of the router advertisement from the access router 109, alteration of the care-of address of the mobile router 203 to CoA2, and switching of the default router from the access router 107 to the access router 109. At this time, the link layer connection point and the default router are both the access router 109. The mobile router 203 notifies the home agent 105 of binding for the home address and new care-of address CoA2 by means of a binding update packet.
The link layer connection points, default routers, and care-of addresses in these states I to IV are summarized in Table 3.
TABLE 3LINK LAYERDEFAULTSTATECONNECTION POINTROUTERCARE-OF ADDRESSIAR107AR107CoA1IINONE(BREAK)AR107CoA1IIIAR109AR107CoA1IVAR109AR109CoA2
As shown in FIG. 22, the state transitions of the home agent 105 during a hand-off are divided into two.
State A: binding for the home address of the mobile router 203, network prefixes within the mobile network 207, and care-of address CoA1 is recorded in the home agent 105. The home agent 105 transfers packets addressed to the stationary host 205 in the mobile network 207, transmitted from the correspondent host 111 inside a stationary network, to the care-of address CoA1. This state continues until a binding update packet providing binding for the home address, network prefixes within the mobile network 207, and new care-of address CoA2 is received from the mobile router 203.
State B: the binding for the home address of the mobile router 203, network prefixes within the mobile network 207, and new care-of address CoA2 is recorded in the home agent 105. The home agent 105 transfers packets addressed to the stationary host 205 within the mobile network 207, transmitted from the correspondent host 111 within the stationary network, to the new care-of address CoA2.
The bound care-of addresses in these states A and B are summarized in Table 4.
TABLE 4BOUND CARE-OFSTATEADDRESSACoA1BCoA2
Next, an example of the state transitions of a conventional mobile host during a hand-off in a third mobile communication system in which the mobile node is a mobile host will be described on the basis of FIG. 23. In FIG. 23, MH indicates a mobile host, AR indicates an access router, and CH indicates a correspondent host.
It is assumed here that a mobile host 401 communicates with a correspondent host 407 on a stationary network. As shown in FIG. 23, the state transitions of the mobile host 401 during a hand-off are divided into four.
State I: the link layer of the mobile host 401 is connected to the access router 403, and the default router is set to the access router 403.
State II: the link layer of the mobile host 401 switches connection point from the access router 403 to the access router 405. The period during this connection point switching is known as a link layer disconnection period. At this time, the default router is still the access router 403.
State III: the link layer of the mobile host 401 is connected to the access router 405. At this time, the default router is still the access router 403. This state continues until the mobile host 401 receives a router advertisement from the access router 405 and switches the default router from the access router 403 to the access router 405.
State IV: this is the state which follows reception of the router advertisement from the access router 405 and switching of the default router from the access router 403 to the access router 405. At this time, the link layer connection point and the default router are both the access router 405. The link layer connection points and default routers in these states I to IV are summarized in Table 5.
TABLE 5LINK LAYERSTATECONNECTION POINTDEFAULT ROUTERIAR403AR403IINONE(BREAK)AR403IIIAR405AR403IVAR405AR405
Next, the state transitions of a conventional mobile router during a hand-off in a fourth mobile communication system in which the mobile node is a mobile router will be described on the basis of FIG. 24. In FIG. 24, SH indicates a stationary host, MR indicates a mobile router, AR indicates an access router, and CH indicates a correspondent host.
It is assumed here that a stationary host 409 in a mobile network communicates with the correspondent host 407. As shown in FIG. 24, the state transitions of the mobile router 411 during a hand-off are divided into four.
State I: the link layer of the mobile router 411 is connected to the access router 403, and the default router is set to the access router 403.
State II: the link layer of the mobile router 411 switches connection point from the access router 403 to the access router 405. The period during this connection point switching is known as a link layer disconnection period. At this time, the default router is still the access router 403.
State III: the link layer of the mobile router 411 is connected to the access router 405. At this time, the default router is still the access router 403. This state continues until the mobile router 411 receives a router advertisement from the access router 405 and switches the default router from the access router 403 to the access router 405.
State IV: this is the state which follows reception of the router advertisement from the access router 405 and switching of the default router from the access router 403 to the access router 405. At this time, the link layer connection point and the default router are both the access router 405. The link layer connection points and default routers in these states I to IV are summarized in Table 6.
TABLE 6LINK LAYERSTATECONNECTION POINTDEFAULT ROUTERIAR403AR403IINONE(BREAK)AR403IIIAR405AR403IVAR405AR405